1. Field of the Invention
The present invention relates to a noise-isolated fastening of an oil sump or pan to a crankcase of an internal combustion engine using an intermediate layer of elastic material.
2. Description of the Prior Art
It is known to provide a rubber interlayer between the oil sump and the crankcase, and to connect these two parts by means of screws or bolts. In this arrangement, the intermediate rubber layer is greatly compressed, whereby the elasticity of the intermediate rubber layer required to reduce noise radiation is at least partly reduced. Therefore, the desired control of noise radiation is only incomplete in this case. Moreover, the use of screws or bolts (bolted connections) does not preclude the transmission of structure-borne noise from the crankcase to the oil sump.
For this reason, solutions have been disclosed where the fastening means are prevented from directly affecting the elasticity of the rubber material in the region which is critical in preventing the transmission of structure-borne noise (see German Preliminary Patents (Offenlegungsschriften) Nos. 27 23 397, 27 53 717, 30 04 426).
The heretofore known solutions suffer from a number of drawbacks. For instance, German Preliminary Patent No. 27 23 397 provides for an intermediate frame which is connectable to the crankcase and which is attached through the intermediary of a rubber-elastic profiled strip to the oil sump. Both the oil sump and the intermediate frame are formed with a shaped flange, the profiled rubber being bonded to these flanges. The intermediate frame and, consequently, the oil sump, are connected by screws or bolts to the flange of the crankcase. In order to avoid excessive tensile stresses in the profiled strip, the oil sump is provided with special stops.
German Preliminary Patent No. 27 53 717 disclosed a profiled frame made of rubber or plastic. Fastening of this frame is effected by means of screws or bolts applied laterally to the crankcase and the oil sump. To support the screws or bolts (this arrangement calls for double the number of fastening screws or bolts), the crankcase and the oil sump are each provided with a bonded metal ring. Furthermore, in order to increase the stiffness of the crankcase, this concept calls for an additional stiffening flange.
The method of fastening proposed by German Preliminary Patent No. 30 04 426 also provides for a shaped rubber or profiled strip, with the connection of the two parts being effected by means of screws or bolts via a so-called retaining plate.
An object of the present invention is to provide a fastening of the aforementioned general type to isolate structure-borne noise, with the inventive fastening, in contrast to the prior art, being distinguished by a more straightforward and simpler design. Moreover, the invention is intended to maintain noise-isolating and sealing effects without any impairment.